A wide variety of screw-in type valve assembly constructions are known which, for example, have a valve body formed with a throttle seat and a valve member that is screwed into a tapped hole in the valve body and formed with a throttle cone for controlling air flow from one air duct to another depending upon the gap between the throttle cone and valve seat. The air flow through the valve assembly is dependent upon the difference between the pressures on either side of the throttle gap defined by the cone and seat, and it is conventional to measure the pressure by means of pressure gauges connected by special lines that communicate with the gap. Monitoring the pressure in such way facilitates adjustment of the valve in accordance with the operating parameters at the sheet delivery station, such as paper quality or speed of the press. For this purpose, conventional manometers have been provided, such as spring diaphragms, or spring tubes or capsule element measuring devices. Such devices are adapted for direct contact with the medium, i.e., air, to be measured, and it is necessary the air pressure be propagated to the measuring spring or the like.